Generalize glXGetProcAddressARB wrapper to work for all wrapper functions

Generalize glXGetProcAddressARB wrapper to work for all wrapper functions

The originally implementation here had a whitelist of function names for
which we would return a wrapped symbol, (a very short whitelist consisting
only of "glXSwapBuffers"). A hard-coded list here would be a maintenance
nightmare.

Instead, we now simply perform a dlsym lookup on the wrapper library itself
and if there's a function that exists in the library matching the name
being requested, we return that.

This way we can add functions to our wrapper library without needing to
change the implementation of glXGetProcAddressARB at all.